J/ApJ/607/60 FIRST-2MASS faint sources (Glikman+, 2004)
FIRST-2MASS sources below the APM detection threshold:
a population of highly reddened quasars.
Glikman E., Gregg M.D., Lacy M., Helfand D.J., Becker R.H., White R.L.
<Astrophys. J., 607, 60-75 (2004)>
=2004ApJ...607...60G 2004ApJ...607...60G
ADC_Keywords: QSOs ; Infrared sources ; Radio sources ; Redshifts
Photometry, photographic ; Photometry, infrared
Keywords: dust, extinction - quasars: general - surveys
Abstract:
We have constructed a sample of bright near-infrared sources that are
detected at radio wavelengths but undetected on the first-generation
Palomar Observatory Sky Survey (POSSI) plates in order to search for a
population of dust-obscured quasars. Optical and infrared
spectroscopic follow-up of the sample has led to the discovery of 17
heavily reddened quasars (B-K>6.5), 14 of which are reported here for
the first time. This has allowed us to define a region in the R-K, J-K
color plane in which 50% of the radio-selected objects are highly
reddened quasars. We compare the surface density of this previously
overlooked population to that of ultraviolet-excess radio-selected
quasars, finding that they make up ∼20% of the total quasar population
for K≲15.5.
Description:
Spectroscopy of our candidate quasars was carried out in the optical
and near-infrared at four different observatories. The majority of the
optical spectra were obtained at the 10m Keck telescopes by using the
ESI and, to a lesser extent, LRIS spectrographs. Optical spectra were
also obtained at the 3m Shane telescope at Lick Observatory.
Near-infrared spectroscopy was performed at the NASA Infrared
Telescope Facility (IRTF) by using SpeX and at the MDM Observatory on
Kitt Peak by using the TIFKAM infrared camera in spectroscopic mode.
We also obtained seven spectra from the Sloan Digital Sky Survey
Spectral database.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 105 69 Optically faint FIRST-2MASS red quasar candidates
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See also:
VIII/71 : The FIRST Survey Catalog, Version 03Apr11 (Becker+ 2003)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/271 : The Guide Star Catalog, Version 2.2 (GSC2.2) (STScI, 2001)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000.0) from FIRST catalog
4- 5 I2 min RAm Right ascension (J2000.0) from FIRST catalog
7- 11 F5.2 s RAs Right ascension (J2000.0) from FIRST catalog
13 A1 --- DE- Declination sign (J2000.0) from FIRST catalog
14- 15 I2 deg DEd Declination (J2000.0) from FIRST catalog
17- 18 I2 arcmin DEm Declination (J2000.0) from FIRST catalog
20- 23 F4.1 arcsec DEs Declination (J2000.0) from FIRST catalog
24 A1 --- Note [c] Individual note (1)
25 A1 --- l_Bmag Limit flag on Bmag
26- 30 F5.2 mag Bmag GCS2 B magnitude
32 A1 --- l_Rmag Limit flag on Rmag
33- 37 F5.2 mag Rmag GCS2 R magnitude
39- 43 F5.2 mag Jmag 2MASS J magnitude
45- 49 F5.2 mag Hmag 2MASS H magnitude
51- 55 F5.2 mag Ksmag 2MASS Ks magnitude
57- 62 F6.2 mJy Fpeak FIRST 20cm peak flux density
64- 70 F7.2 mJy Fint FIRST 20cm integrated flux density
72- 75 F4.2 mag J-K J-K colour index
77 A1 --- l_R-K Limit flag on R-K
78- 81 F4.2 mag R-K R-K colour index (R magnitude from GSC 2)
83- 87 F5.3 --- z ? Redshift
88 A1 --- n_z [e] Note on z (2)
90-100 A11 --- Type Type of object
102 I1 --- Ref [1/3]? Reference (3)
103 A1 --- n_Ref [bd] Note on Ref (4)
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Note (1): c:
This object had a FIRST-APM separation of 5.77" and was identified as
an extended source by the APM machine's scans of both the O and E
plates. These data gave the objects a 54% probability of being
associated with each other. Our criterion of 94% reliability,
discussed in Sect. 2, allowed this source to remain a candidate. Its
extended radio morphology, as well as optical magnitudes and spectrum,
suggest that this object is the contaminant allowed by our survey
statistics.
Note (2): e:
We determined the redshift from Hα, which lies between the H and
K bands; its signal was strong enough to be detected in the region of
telluric absorption. We also used a weaker Hβ line also residing
in the telluric absorption region between J and H. This allowed us to
identify Mg II absorption in the optical spectrum at this same
redshift. Smith et al. (2002, Cat. J/ApJ/569/23) obtained an
independent redshift measurement of z=1.800 for this object using
Hα alone.
Note (3): References as follows:
1 = Gregg et al. 2002, Cat. J/AJ/112/407
2 = Smith et al. 2002, Cat. J/ApJ/569/23
3 = Lacy et al., 2002AJ....123.2925
Note (4): Notes as follows:
b = SDSS optical spectrum
d = This object was initially classified as an emission-line galaxy,
based on its optical spectrum. The near-infrared spectrum reveals
a red continuum and a broad Paβ line. See Sect. 4 for
further discussion.
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History:
From electronic version of the journal
(End) James Marcout, Patricia Vannier [CDS] 06-Jul-2004